Device for admitting preheated secondary air into furnace fireboxes



Nov* 15, 1949 E. L. WIEDMAN DEVICE FOR ADMITTING PREHEATED SECONDARY AIRINTO FURNACE FIREBOXES Filed July 28, 1945 Patented Nov. 15, 1949 UNITEDSTATES TENT OFFICE DEVICE FOR ADMITTING PREHEATED SEC- ONDARY AIR INTOFURNACE FIREBOXES 1 Claim.

My invention relates to improvements in fuel saving devices, and moreparticularly to that type designed to preheat air while being introducedinto the combustion chamber of a boiler or furnace to cause thepreheated air to commingle with the products of combustion and thusfacilitate the burning of unconsumed and escaping gases rising from theburning fuel.

The object of my invention is to provide an airheating device designedto be attached to the door closing the fuel-feed opening in a boiler orfurnace so as to project into the combustion chamber of the latter whenthe door is closed, it being so designed that the air drawn into thedevice is caused to travel through a circuitous path and to compel theair in its path through the device to come in contact with the maximumheating surfaces and retard the ow of the preheated air therethroughwhile separating the same into small volumes to assure maximum heatingeifect.

It is also the object of my invention to provide a device of this kind,the body portion or casing of which can be cast and in which the minimumof machining is required so as to provide a simple and inexpensivedevice readily installed to the door of the fuel-feed opening of aboiler or furnace or in the wall of the latter so that preheated air isdelivered over the burning fuel.

In the accompanying drawings illustrating my invention in what I nowconsider its most aplproved form,

Fig. 1 is a central longitudinal section through the device, showing thesame applied to the door of a boiler or furnace closing the fuel-feedopening leading to the combustion chamber or iire box.

Fig. 2 is a transverse section taken on line 2 2, Fig. 1, looking towardthe right.

Fig. 3 is a transverse section on the same line, looking to the left.

Fig. 4 is a transverse section taken on line 4 4, Fig. 1, looking in thedirection of the arrow crossing said line.

Fig. 5 is a transverse section taken on line 5 5, Fig. 1, looking in thedirection of the arrow crossing said line.

The device comprises a housing or casing 6 which is preferably cast intwo parts 'I and 8, connected together in a manner to be hereinafterdescribed to form a unitary structure.

Medially this housing is cylindrical, as at 9, and at its attaching orouter end it is enlarged, as at I D, to form a bell-shaped terminal, orexpansion chamber as it may be termed. The inner or free end of thehousing or casing is of 2 bulbous formation and gradually enlarged fromthe medial cylindrical portion 9. This bulbous portion is designated bythe numeral II and serves also as an expansion chamber. In the region ofthis bulbous portion the two parts l and 8 of the casing or housing areconnected to' closed by an end Wall I4 having a hub I5 and spacing lugsIS lying in contact with the inner surface of the door II closing thefuel-feed opening leading to the combustion chamber of a boiler orfurnace in which -coal or other similar fuel is used to generate heat.Extending through the door I'I isa pipe I8 which is threaded into thehub I5 of the casing and to the outer end of this pipe an air-inlet headI9 is threaded, it having a chamber 20 in communication with theinterior of the pipe I8 and numerous air-inlet openings 2i leading tosaid chamber. This air-inlet head also serves as a nut to tighten thedevice against the inner side of the door I1. An air-inlet pipe 22 isalso threaded into the hub I5 from the inner side of the casing and thispipe trends lengthwise and axially through the major portion of thecasing or housing. Pipe 22 serves asa continuation of pipe I8. A singlepipe may, therefore, be substituted for the pipes I8 and 22 so long asit is securely fastened within the end wall lll of the casing andextends through the door I'l a sufficient distance for attachment of theair-inlet head I9 thereto. The pipes I8 and 22 may, therefore, beconsidered a continuous air-inlet tube, the outwardly projecting portionof which serves as a means to attach the device to the door Ii or topass the same through an opening in the Wall of the combustion chamberof the boiler or furnace. Broadly considered, the door I1 serves as aportion of the wall of the combustion cham- .ber and, therefore, wherehereinafter reference is made to the wallof the combustion chamber, itis to include the door I1.

Cast Within the part 8 of the casing at or near its inner end is abridge member 23 so constructed that air passing through the casing willpass around this bridge member, and in the drawings I have illustratedsegmental openings 2d at opposite sides of the bridge member for thispurpose. This bridge member is recessed on its outer face and into thisrecess is threaded or other- Wise' secured an air-return pipe 25surrounding and concentric with the air-inlet pipe 22 and spacedtherefrom to form an annular air passage 26 between the two pipes, ortubes as they may also be termed. By reason ci its attachment to thebridge member 23, this air-return pipe is closed at its inner end andits outer end is open and terminates in spaced relation to the end wallI4 of the casing. i In the enlarged outer end of the casing anannulariange 27 is cast and projecting from the end surface of thisangeare heating fingers or elongated nubs 28 which trend outwardly or towardthe open end of the air" return pipe 25. These ngersorjriiihs"are'spaeedapart circumferentially and sirieeftheyare 'fornieii integral with thewall of the casingithey become well heated due to the fact that'the'yare disposed directly over the burning fuelwitl'iinthefc'om bustionchamber.

nubs 29 project and thse also trend towardthe (.pe'n end` of the'return' pipeVlr 25 The iingers`29 are preferably disposed at a greater'angle 'to the axis of the",d casingthan thev fingers or nubs: 28and'they are; s taggeredwith relationtothe latter, being posi'tioriedinY linewith the spaces betvienusaidfingers*'28?` 'I hen'gersor nubs/29 are, therefore;jalfsofina-v circular series. y l

the outer suriarlsed of theA bridge-inember 23faiircularrserie i o'ffheating vngers or ,elongated nubs@ BDeXtend'and'ithey are spacedfromthe air-return pipe 25, a s best shown in Fig. 1.v VSurrounding thecircular seriesI of fingers or'n'ubs 30 isk a i circularseriesioilheating fingers for elongated nubs 3l which extendinw'ardly`or .toward the'rairf esca-peend ofthedevice".` ,'Ihengers or nubs 31|of the seriesfaren spaced apart; and spaced' outwardly froml thebuttendfscf`-tlieV lattera ciricular series ofheating ngers ornubs 32'isarranged. These Iare` also'spa'c'ed apart and staggered with respecttothengers lZitlfand 31.

vIt is -to be noted that y the v.free en-dsjof'-l the ngers or nubs '30terminate in'theiannular space between-'the' circularseriesfofiingers3f]` 'and 32.'

Projecting `outwardly from thennjeij lsuriaeepf the'ipart 8 of5thecasing are two' circular series r of fingers 33, '34wihich surround:airesca'pe'area 35"from whichfpreheated lair escapesthr-ougfhfacircular 'series pfff Iai` i escape' openings 36" formed inthjeipart-o'ftheicasing. y i

V'ru clarifykv thejiterms' inwardly and foute w-ardly, Lconsider-thatfend ofthe deviceseoured to thedoor I1 and: receivingrth'eatmospheric air to bethe outer end and the air-discharge or: op'-po'sit'e end'tobe the inner end.

Ima-device ,ofl this generaltype'airtalenfin n one'end", heated, `an-ddischarged over'th'elburniiig fuelA at the other endf' 'Ihenaturalfdifaftfcreated 'byv the communiationwestablished between "thecombustion chamber and 'thelchiiijin'ey-1to which theiboileror'turnacei's 'connected fcreat'e's ia rent 'ofV air through the deviceiW'heni thev fifre in the combustion chamber is burning;- the" deviceisheated byreason of its beingvr locateddirectly above-the burningiuel.,v Air 'passingthroighthe device entersthe inlet openings inthefair'linifet in its course through the'"device; The '-dii'etibn From theinner side giri-,he Y ange additional heating fingers or elfngatid..

4 of the passage of iair is then again reversed so as to travel in thesame direction as the :air passing through the air-inlet pipe 22, comingin contact, whil-e being compressed in the restricted end of thebell-shaped terminal or expansion chamber l0, with the two annularseries `of heating lingers 28, 29, which project inwardly from theannular flange/2,1 located rat the receding portion of the Wall of saidvexpansion chaginber', the; air being thus lthoroughly heated and the'vair' current broken up by contact with the considerably augmentedheating surface Iprovided yby the ngers or nubs 28 and 291' Afterpassing these ngers lor nubs thelair is further, compressed in themedial restrictedgportion 9 of the casing rand retarded in its" passage"through the device, with the result that lal moreecient preheating ofthe same is assured. After passing through the medial restr'icte'd;portion of the device, or compression chamber as it may be termed, itag-ain encounters, in: successive order,` the heating in'ger-'sior'-nbs3`2; '31' and 30, which are' staggeredwithl respect to eachotheriandare'located' with'ina gradually widening portion'of the casingsov that a complete breaking 'up of the ia'i'r ciirrer'it isaissuredWhile the 'airisv again-.under expansion.; Againdn pass.- ing'throughthis p'ortiri'of the larcu'rreni', path provided in the? device`,l'itcomes inoontact 4with a' greater augmentedhea'tin'g 'surface`l and due"to the many fingers ornubsi'provided'and Yiiieea'use ortrrejeombired"superrciai'areas cfthese nubs exceeding' manytiniesfthesupetcial area'r offth'e partsvfroi'iif'which theyY project,a* considerably higher temperature i'sf prcvidedio'r the airias itapprdachesitsrregi'on o'f escape.

After' passing" through the nngerf or mib area. containing the nubs-'32;311'and130gthe'air' ypasses through the seg-'mental' op eningsf'za: inyth'en bridge member: Zavyherethe greatesty diameter -o'if the bulbous'inner endor'headiof.thefdevicefis` located. The" 'air then? in 'highlyheated forin passes'between the two circular ser-ies off g'ers '33 and3l and' reaches ther-air escape area 136' surrounded by' saidi1ast-iinentionedA fingers.. fin-ally?. escaping through the ai'r escapeopenings 35Fin the'fbulbous inner ender headofthe'device.'

It will'beapparent from the foregoing that the air inpassingtl'noughtheirdevicelis given'a cir'- cuitous' course and'ithat' at twofpoints in its' course it passes through' expansioniregion's vand alsothrough a compression region betweenthe expatrision"regionis.. Alsdby.reason' of the factjthat comparatively longv fingers* or nubs extendiriwardly from the"wa11"of".thev` casing or housing,

which latterfis"thoroughlyheate'd by 'the burning fuel, :these ngers .ornubs are likewise heated` and preheat'ingcontact surfacesAareJprvided"greatly exceeding in superficiali 'areas-thel :annular orcir'- euiar'regions' froiii'whieuthey' reject:` Btl-reason -of thefingers `or nubs being 'slaggerdwith respect 'to each" other;l the'airicurren't's-L are-'divided *onryto' come 'together'again"afoie bodyunder compression by passing through-arsticted -arerafals'o by reason ofatleast/brie annlar'series `of angersY or nubs being formed." -on'ajgadualiy restricted wall portion prior to pas'siii'gtlouh a 'restrictedarea,v the llow' ofthe air` througl'il the device is retarded'and;'thereicre,"subicted'tb the' high temp erature 'within thed'e'ivioef'over a longer periodici 'timefthaii "wouid' otherwisefiiiepessime. ,i

'nrief'preiieatifig 'eff'the'lairz'isgreatiy increased @by reason of"'the heatngffiigrs for" hubls bei-rig located atapliurfaglityY fof'regidiisad especially 'Sirce two-'f these 'regiii"a1'e=`l0oted"`at O1?'i' the air escaping end of the device, where the in- ,terior of thedevice is subjected to greatest heat. As the air escaping from thedevice comes in contact with the unconsumed products of combustion,these are ignited and thus consumed pass off in the usual manner throughthe chimney to which the boiler or furnace is connected after havingutilized the maximum heat created for the purpose intended.

It will be apparent from the foregoing that :my invention is subject tomany changes in construction and design without departing from thespirit of the same or sacricing any advantages thereof while adhering tothe scope of the invention as disclosed in the following claim.

What I claim is:

A fuel saving device for furnaces or the like, comprising a. tubularcasing fastened at one end to the wall of a combustion chamber andprojecting inwardly therefrom into said chamber, said casing having itsfastened end enlarged to form an expansion chamber and its opposite endenlarged to a lesser degree to form a second expansion chamber, anair-inlet :pipe extending axially into said casing from the fastened endthereof and having an air-inlet head outside of said casing throughwhich air enters said pipe, said airinlet pipe being open at its innerend, an air- 6 return pipe having a closed end confronting and spacedfrom the open inner end of said lair-inlet pipe and having its oppositeend opening into said mst-mentioned expansion chamber, two series ofheating ngers extending inwardly from the wall of said first-mentionedexpansion chamber and having the fingers of one series staggered lwithreference to those of the other, and heating fingers extending from thewall of said second expansion chamber and staggered with respect te eachother, said second expansion chamber having air-escape openings throughwhich the heated air escapes aiter contact with the various heatingfingers Within ysaid easing.

EDWARD L. WIEDMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,267,295 West May 21, 19181,482,104 Van Daam Jan. 29, 1924 1,578,151 Marsh Mar. 23, 1926 1,717,421Van Daavm June 18, 1929 1,733,901 Owen Oct. 29, 1929

